This invention relates to a mechanism for controlling the movement of a hydraulic ram of the type which is used in conjunction with forming glassware in a mold of a glass making machine.
One common type of glass making machine utilizes a vertically reciprocal ram or plunger which is movable to a molding relationship with a mold member, at a fixed position relative to the ram, so that the molten glass contained within the mold is formed between the ram and the mold to provide a glass product of the desired shape. In such machines, it is conventional for the ram to remain in engagement with the mold until such time as the glassware is properly cooled and in a set or rigid condition. The ram is then raised from the glassware and the table carrying the mold is indexed to another position, as for cooling or to the take-out position. An open mold is then moved into position below the ram for forming another glass product of the desired shape. Each cycle of operation of the ram involves a downward movement of the ram into the mold area, a rest period in the mold area to allow time for the ware to properly set, and an upper dwell position while the mold with the formed glass product is moved away from the position below the mold and while the next mold is moved into position for the formation of a glass product or ware therein by the ram.
These machines generally have a predetermined production rate which means that each ram has a predetermined time period to complete its up-down cycle. It is generally considered to be desirable to hold the ram within the mold for as long a period as possible so as to better form the product without the distortion and without wrinkles developing thereon. In other words, the longer that the ram is in the mold, the longer the time there is for cooling and setting the ware to provide the improved product. Since the time that the ram is in the mold is only a fraction of the total up-down cycle time for the ram, any increase in the time required to move the ram to and/or from the mold can be used to better advantage by using the saved time as dwell time for the ram in the mold for providing an improved product. It is clearly highly advantageous to increase the time that a ram is in a mold without increasing the overall cycle time of the machine or of the ram.
In order to produce formed glassware products of high quality, relatively high pressing or ram forces are generally considered desirable in order to hold the ram in firm engagement with the mold during the time that the ware is being formed between the ram and the mold. One way in which this is sometimes accomplished is by means of a toggle mechanism which increases the ram force while still using a smaller initial force in the toggle operating cylinder. Toggle mechanisms, however, are generally considered to be expensive and require more maintenance than is desirable in a glass making machine.
It is also considered advantageous in glass making machines to provide ram motion which is adjustable and provides a constant speed pressing action as the ram comes into contact with the molten glass being formed. Another factor that is considered important in the formation of glass product, in a glass making machine of the described type, is the gradual movement or easing of the ram out of the formed glass product in order to prevent distortion of the glass product.